Production of regenerated cellulose filaments from wood pulp



May 15, 19 w. L. DEAN ET AL PRODUCTION OF REGENERATED CELLULOSEFILAMENTS FROM WOOD PULP Filed July 51 1959 ATTORNEY6 3,634,910PRGDUQ'HQN h REGENERATED QELLULGSE FKLAMENTS FRQM WQQD PULP Walter L.Dean, Arthur M. Dowel], 31"., and doseph flames, In, h lemphis, Terms,assignors to The Buckeye Cellulose Corporation, Cincinnati, Ghio, acorporation of ()hio Filed luly 31, 1959, her. No. 8365889 6 Claims.(Cl. lilo-165) This invention relates to improvements in the manufactureof regenerated cellulose filaments from prehydrolyzed sulphate chemicalwood pulp by the viscose process and has for an object the provision ofa novel method of controlling certain significant characteristics andproperties of the viscose and of the filaments produced therefrom. Moreparticularly, the invention is concerned with the preparation of viscosewhose composition can be altered, Without affecting filtrationcharacteristics, by the addition of one or more of a family of certainnovel alkylene oxide esters of disproportionated rosin in which theethylene oxidc-LZ-propylene oxide ratio may readily be altered toproduce in rapid sequence, if desired, filaments varying Widely in skinto core ratio and cross-sectional shape. Themembers ofthesaid family of'additive compositions are completely compatible with each other andwith the conventional coagulating and regenerating agents employed inspin baths. It is thus possible in accordance with the present inventionto control the cross-section and skin to core ratio of rayon filamentsby choice of the novel ester employed and to do so Without alteringviscosefiltration characteristics, and if desired, without interruptionof processing.

in order to appreciate the full significance of applicants improvementin the controlled fiber modifyingaction on rayon filaments, someunderstanding of the processing of ire-hydrolyzed sulphate chemical woodpulp to rayon by ments thus produced is required.

Viscose is a highly complex system consisting of a dispersion ofcellulose xanthate in a dilute aqueous sodium hydroxide solution, whichsystem is constantly undergoing change as a consequence of therearrangement of xanthate groups and a gradual breakdown of celluloseXanthate, a change commonly termed, ripening. At a particular degree ofripeness, the viscose is spun into filaments and regenerated.

The conditions under which viscose is spun have a profound elfect on thequality and characteristics of the raythe viscose process and thepropertiesofthe rayon filaon filaments so obtained. A large number ofvariables that affect rayon quality have been discovered in the past andmethods for controlling many of these variables have been discovered.Viscose, after'fiitration, was, in the" earliest methods of carrying outthe process, ripened and extruded into an all acid bath whereby thealkali contained in the viscose was neutralized and the cellulosexanthate was decomposed by splitting away the xanthate groups which madepossible the initial solubilizing or dispersement of the cellulose.After washing the extruded product free of residues and decompositionproducts and drying, the rayon fibers were obtained.

According to later developments a zinc salt is incorporated in the spinbath to retard regeneration following i and during the coagulation ofthe viscose rayon filaments, and it may be possible that other salts ofbivalent metals would accomplish the same purposes. Recognition of theseparate functions of coagulation and regeneration together withimproved techniques for controlling the stretching of the yarn duringthese operations has led to rayon of much improved strength. Immediatelyupon coagulation of the viscose, which results in a gel cellulosexanthate in filament form, stretch is imposed on the yarn to cause auniaxially orientated structure which results in the aforementionedimprovement in fiber strength. The incorporation of the zinc ion intothe spinning bath is believed to retard regeneration by transformingsodium cellulose xanthate into zinc cellulose xanthate. The greaterstability of the zinc cellulose xanthate in acid media as compared withthe sodium cellulose xanthate then slows the regeneration stepsufiiciently to allow uniaxial orientation of the filaments bystretching in the gel state. The coagulated viscose yarn is then fullyregenerated by continued exposure to the acid bath or by utilizing asecond hot acid oath; additional stretch may be imposed during this andsubsequent hot Washing steps. Although the regeneration of cellulosexanthate proceeds very rapidly, the presenceof zinc ion in the spin bathand a regeneration retardant (chemical modifier) in the viscose markedlyafiects the relative speeds of penetration of the hydrogen and zinc ioncomponents of the spin bath. Thus there results a much more extensiveformation of the more stable zinc cellulose xanthate salt which mayactually occur throughout the entire filament ahead of the decompositionof the sodium cellulose xanthate at the concentration of acidnormaliyemployed in spinning baths. In this manner a uniaxially orientedstructure is achieved before complete regeneration takes place.

Normally in coagulation and regeneration the surface (skin) of thefilament is fixed and there is developed a tubelike structure consistingof an outer skin of regenerated cellulose together with an inner core ofviscose as the viscose on the outside ofthe filament is regenerated, andthe cellulose separates itself from much of the water initially presentin the viscose (which normally contains only about 643% cellulose).fter'washing to remove the decomposition products, the filaments aredried, and during this step, depending on the combination of spin bath,chemical modifier and stretching employed during regeneration, thesurface becomes more wrinkled or crenulated due to stresses set upbetween the skin and the interior sections of the fiber as the tube-likeskin structure of the filament collapses upon removal of water.

Certain chemical additives, usually surfactants, when contained in theviscose or added to the spin bath have been found very useful withrespect to regulating the regeneration rate and/ or the diffusion ofacid into the interior of the filament, whereby the regeneration rate isretarded to allow a high degree of uniaxial orientation prior to thecompletion of regeneration. Such filaments, referred to hereinafter asmodified filaments, are characterized by relatively smooth surfaces andgenerally beanlike, or round, cross-sections which dye rather uniformly(depending on the degree of fiber modification). The linear polymers ofethylene oxide are outstanding in their ability to promote this type ofstructure, but result in completely modified fibers withoutaifording'the rayon manufacturer the opportunity of obtaining theparticular degree of modification desired by selecting an additive fromamong those of a family of additives having the same chemicalconstituents but in varying proportion. Even with the ethylene oxidelinear polymer moiety is combined with a second base material, such asto give polyethylene oxide others, esters, amines, etc., there persistsa high degree of filament modification as indicated by microscopicexamination. In contrast to this lack of control, the'advantages of themodified type of filament are enhanced through the use of the family ofadditives of this invention by making possible various combinations ofhigh strength, high flex life, resistance to abrasion, resistance tomoisture, and improved dye fastness which can be easily engendered infibers modified in this filaments may give rise to processingdifiiculties. If one additive is replaced by another to impart to thefilaments a different degree of modification or skin to core ratio, andthe two additives are not compatible, the equipment and especially thespin bath must be purged before the second additive is introduced,necessitating interruption of processing. Also the incorporation ofdifferent types of chemical additives in succeeding batches of viscoseto be processed 'in order to vary the fiber properties may givedifficulty by causing a change in the filterability level attained andthus deprive the processor of the advantage of always maintaining highfilterability while attaining specific combinations of filamentcharacteristics.

It is therefore an object of the invention to provide a family of novelchemical additives affording progressive modification of filamentcharacteristics over a wide range, the additives being fully compatiblewith one another in the steps of viscose processing whereby filaments ofdifferent degrees of modification over a wide range may be obtainedwithout the use of supplementary additives to increase filterabilityand, if desired, without interruption of processing.

These and other objectives are achieved by incorporating in the viscose,preferably by addition to the sheeted prehydrolyzed sulfate chemicalwood pulp to be used in the viscose process, as a modifying agentcapable of controlling the skin to core ratio and cross-section shape offilaments spun from the viscose, of an ethylene oxide-1,2- propyleneoxide ester of disproportionated resin in amount from 0.5% to 3.5% basedon the bone dry weight of the pulp, the oxides being present in theesters in amount from 1.5 to 9 times the amount of rosin by weight, andthe ethylene oxide constituting from 40% to 85% of the total oxideweight. The present applicants found that the skin to core ratios andcross-sectional shapes of filaments are increasingly modified withincrease in the ethylene oxide percentage in the total oxide weightwithin the indicated range, and that variation of the percentage doesnot adversely affect the high viscose filterability. As mentioned above,the variation in fiber modification is achieved by variation of theethylene oxide percentage in the ethylene oxide-1,2-propylene oxidegroup within the compounds. All of the compounds within the 1.5 to 9total oxide to rosin ratio are operable in practicing this invention.Moreover, filament characteristics may be readily and continuouslyvaried over a wide range by substituting prior to spinning viscosecontaining one agent of the group with viscose containing another agentof the group having a different ratio of oxides, without interruptingthe process or spraying the system.

Applicants also noted that minor variations in fiber modification areachieved by increasing the ratio of total oxides to rosin from 1.521 to9:1. It was also observed that increased usage of a given surfactantwithin the disclosed group from 0.5% to 3.5% resulted in a greaterdegree of fiber modification and that a small effect on fibermodification may result from the selection of ethylene oxide terminal asversus 1,2-propylene oxide terminal agents in sequential compoundshaving the same overall composition. It has been found, however, that asto changes of composition within the agents, the greatest effect infiber modification is achieved by varying the ethylene oxide percentagein the total oxide employed.

Further objects and features of the invention will be apparent from thefollowing description of the preferred practice thereof, and from theaccompanying drawing in which FIGURES 1 to 3 represent photomicrographsof sectioned fibers, stained to distinguish the skin and core portions,illustrating the controlled modification achieved by the use of chemicaladditives selected from the family of chemical additives havingdifferent ratios of ethylene oxide to 1,2-propylene oxide and totaloxide to disproportionated rosin base.

As has hereinbefore been indicated, this invention contemplates themanufacture of regenerated cellulose fibers 1 chanical and hydraulicmeans.

from prehydrolyzed sulphate chemical wood pulp by the viscose processwith the use of a particular family of chemical additives to controlfiber modification while maintaining at each degree of fibermodification the high viscose filterability necessary to economicprocessing in the viscose industry.

In the prehydrolysis operation, wood chips or other lignin-containingcellulosic material, are conventionally treated with water, steam ordilute acid solution (up to about 0.3% solution of acid), at from about300 to about 375 F, and at pressures greater than atmospheric, forreaction times up to about 120 minutes prior to digestion. Thistreatment is carried out under acid conditions which are preferablyinduced by the addition of an acid such as, for example, acetic, citric,nitric, oxalic, phos phoric, sulfurous (sulfur dioxide), sulfuric orcombinations of these. Alternatively, if it is desired that no acidshall be used, and provided no alkaline agents have been added, an acidcondition will develop as a result of the hydrolysis of the cellulosicraw materials being treated. At the end of this treatment, thehydrolysis liquid is drained oif, and the remaining solid material maybe washed in situ, or the cooking liquor for the next step may be addeddirectly without washing.

The hydrolyzed lignin-containing material is then pulped by the sulphateprocess wherein the active digesting ingredients are sodium hydroxideand sodium sulfide. This process is well known to those skilled in theart and any reference to the sulphate method of digestion appearingherein or in the appended claims refers to digestion wherein the activedigesting ingredients are sodium hydroxide and sodium sulfide. Aftersuitable. bleaching the purified cellulose is sheeted and dried to formthe prehydrolyzed chemical sulphate pulp mentioned herein.

As is well known in the art, in the production of viscose by theconventional sheet steeping method, dried sheets of pulp are placed in asteeping press and steeped in a solution of sodium hydroxide, normallyhaving a concentration from about 17 to 20%. The caustic soda solutionis usually introduced at the bottom of the enclosure at such a rate thatit rises along the sheets in the direction of the predominant lengthwiseorientation of the pulp fibers at a rate equal to the rate of riseinduced by the capillarity of the pulp. The operation is generallyconducted at temperatures of from about 20 to 25 C. After about one hourimmersion, the excess sodium hydroxide solution is drained off and thesteeped pulp is pressed to obtain the desired alkali cellulosecomposition. The alkali cellulose is then reduced to crumbs in ashredder. This latter mechanical action proceeds for about one to twohours.

The continuous or slurry process of steeping differs from theconventional process in that the pulp is fed into a tank of concentratedcaustic soda solution at a uniform rate. There it is reduced to a slurryof fibers by me- This step usually is conducted at temperatures aboveambient temperatures, up

to 65 C. with the higher temperatures being preferred because of theresulting accelerated rate of alkali cellulose production. After anaverage treatment of about 15 minutes, the slurry of fibers is forced bypressure between rottaing rolls which are slotted or otherwiseperforated to permit drainage of the caustic. The pressed cake of alkalicellulose is then reduced to crumbs, generally on one of the two typesof machinery conventionally employed by the art, i.e., a one-passGarnett roll type shredder or a disk refiner type shredder. Continuousshredding permits substantially instantaneous shredding of alkalicellulose by one passage of the alkali cellulose thru a stator-rotorarrangement of the shredder which may be either of disk or roll design.The Sprout- Waldron refiner is an example of the disk type shredder ascompared to the Garnett roll type shredder. The disk refiner normallysubjects alkali cellulose to much less severe mechanical action than isthe case with a high speed roll type shredder.

Beginning with the alkali cellulose crumbs, the continuous and theslurry processes are essentially the same thru the regeneration step.

The alkali cellulose crumbs are aged under carefully controlledconditions. Here, by means of alkaline oxidation, the average molecularchain length of the cellulose is reduced to a level that will produce aviscose having the desired solution viscosity. After aging, the alkalicellulose crumbs are mechanically mixed with the proper proportion ofcarbon bisulfide, which combines chemically with the alkali cellulose toform cellulose xanthate. Upon addition of dilute hydroxide solution in amixing device, the orange colored cellulose xanthate crumbs dissolve andform the viscose solution known as viscose.

The viscose solution is then filtered and deaerated. During filtration,foreign particles and undispersed gels are removed by the use of severalsuccessive filter media. Completely undissolved matter, While importantto the yield, does not ordinarily affect filterability seriously.Rather, the imperfectly dispersed cellulose, the gels, which plug thepores of the filter media, have a much greater adverse effect. A poorfiltering viscose leads to many costly interruptions of the process byrequiring frequent replacement of the filter media. Therefore, theviscose manufacturer requires a filterability level which permits a highproduction schedule with attendant low cost in labor and filtermaterial.

During the filtration and deaeration operations the viscose is ripenedat a controlled temperature. In this ripening step, complex chemicaland, colloidal changes occur which impart to the viscose certain desiredqualities which have a profound influence on the character of the rayonfiber product later regenerated from the viscose.

Regeneration into filaments or films is accomplished by extrudng theripend viscose through the very small holes of a spinneret or through aslit, depending upon whether a fiber or film is desired, the saidextrusion being made into a bath containing sulfuric acid and salts inaqueous solution. The action of the spin bath results in coagulation ofthe viscose and subsequent regeneration of the cellulose, thus formingcontinuous solid filaments or films. Various washing and chemicaltreatments are applied to the regenerated filaments or films in order toremove residualchemicals therefrom, bleach the cellulosic material,andimpart desirable properties to the finished product. p

As hereinbefore explained, the filaments are stretched as regenerationproceeds, and the opportunity for resultant orientation of the fiberscan be altered over a wide range by incorporating in the viscose anappropriate modifying.

agent selected from the described family of agents, without interruptingthe process. v

The spin bath may contain from 3% to of zinc sulfate, from 5% to 10% ofsuphuric acid and from 10% to 23% of sodium sulphate in aqueoussolution. It will be appreciated, however, that the inventioncontemplates the normal practice of viscose processing, except for the 7chemical additive employed, and that the processing details form no partof the instant invention. These details therefore may be varied widelywithin the limits of accepted practice.

The chemical additives employed in the present invention are prepared byreacting disproportionated rosin randomly or sequentially with ethyleneand 1,2-propylene oxides in varying amounts. The disproportionation ofrosin is effected by heating gum resin (-tall oil) to an elevatedtemperature, for instance, over 200 C. for an extended period, in thepresence of a suitable catalyst such as palladium on carbon. In effectthe reaction consists of the removal of two atoms of hydrogen from theconjugated double bond abietic-type acids and the rearrangement of thedouble bond system to form an aromatic nucleus in the production ofdehydroabietic acid. The hydrogen that is removed is readily absorbed byother conjugated double bond abietic-type acids present to produce thestable dihydroabietic and tetrahydroabietic acids. The product containsa major'proportion of dehydroabietic acid, and in minor proportion,dihydroabietic acid and tetrahydroabietic acid. 5 l V Disproportionatedrosin is commercially available, one such product being manufactured andsold under the trade designation Rosin 73 l-D. This commercial product,sometimes called technical dehydroabietic acid, is described as a pale,moderately hard thermoplastic rosin,

having an acid number of 153, a softening point of 81 C.,

and a density of 1.058 atZtl" C.

In the preparation of the esters, disproportionated rosin is reactedeither with a mixture of 1,2-propylene oxide and ethylene oxide invarying proportions as indicated hereinbefore, or with 1,2-propyleneoxide and ethylene oxide sequentially, with either the ethylene oxide orpropylene oxide being terminal. In the first instance the arrangement ofthe ethylene oxide and propylene oxide units is completely random. inthe latter instance, the ethylene oxide units and propylene oxide unitsare arranged in two unitary blocks, and the ethylene oxide-1,2-

propylene oxide portion of the structure is generally referred to as ablock polymer. The reaction is carried out in a jacketed vessel in thepresence of sodium hydroxide as a catalyst, at temperatures well knownin the art. The preparation of the rosin esters forms no part of theinstant invention, and the processing details may bevaried within thelimits of conventional practice in the preparation of the esters of theacids oi disproportionated rosin.

Modifying action as-hereinbefore described may be obtained by inclusionin the viscose process of small amounts of the order of 0.5% based onthe bone dry weight of the pulp, but amounts ranging from 0.5% to 3.5%will give the described performance. Addition of v the chemical additiveat any convenient stage in the viscose process prior to spinningwillresult in the modifying action, and addition prior to completion ofthe steeping operation in the slurry process and prior to the completionof shredding in the conventional sheet steeping process will in additionresult in viscose possessing a high degree of filterability. Addition ofthe chemical additive to the prehydrolyzed sulfate chemical wood pulp isquite satisfactory as is customary with other types-of additives.

All of the esters of this invention in which the oxides are randomlyarranged and many of the esters with seqential oxide arrangement areliquid, and are thus conveniently and economically shipped, handled, andused. Greater resistance to alkaline saponifica-tion' is exhibited bythe mixed oxide esters of this invention than by the simple ethyleneoxide esters of the prior art and the rate of Water solution and/ordispersion is greatly enhanced by the presence of a proportion ofpropenoxy groups in the oxide chain, resulting in improved stability andgreater ease of application. Excellent filterability is provided bythese agents regardless of the variation in the percentage of ethyleneoxide in the total oxide, namely 85% to 40% by weight.

The effectiveness of the chemical additives in controlling the skin tocore ratio of filaments isreadily demonstrated by subjecting filamentsections to a dye process to differentiate between the skin and coreareas and show the cross-sectionalshape. In order to do this, thefilaments are embedded in paraffin and six micron cross-sections are cuttherefrom using an American Optical Company sliding microtome. The soprepared sections are then fixed on a microscope slide by an albuminfixative and the paratiin dissolved in xylene. The slide with the fixedsections is flooded with a 10% aqueous solution of Solop enyl Fast BlueGreen BL dye and steeped for 40 seconds in a beaker on a hot plate. Theexcess dye is next washed away by dipping the slide into a beaker ofWater. Reference to this procedure for dying the core section of afilament cross-section while leaving the filament skin unstained may befound in Textile Research Journal, vol. XXIV, No. 397 (1954).

The-differentially dyed filament cross-sections prepared in the mannerof the preceding paragraphs were microscopically examined and recordedfor comparison by photographic media using a visible light microscopewith a 6-15 (orange) filter. The following microscope optics wereused: 1) An achromatic NA 1.25 condenser, (2) a 4 mm. NA 0.95apochromatic objective, and (3) a x Leitz Periplan ocular. The finalmagnification obtained on the photographic prints of the filamentcrosssection was about 500x.

The enlarged photographs of the prepared transverse cross-sections ofthe filaments reveal clearly the extent of skin area, as illustrated inthe several figures of the accompanying drawing. In such photographs theundyed skin areas of the filaments sections appear light and aresubstantially colorless whereas the dyed core areas are.

dark. As will be hereinafter more fully described, the several figuresof the drawing represent actual photographs of sectioned filaments dyedas described, the filaments in each figure being spun from viscosehaving incorporated therein identical amounts of a selected agent of theclass to which the invention relates, differing from the chemicaladditive employed in the processing of the filaments in the otherfigures only by the percentage of ethylene oxide in the ethyleneoxide-1,2-propylene oxide group of the ester contained therein. Theextent of modification efir'ected by each of the selected agents isclearly observable, ranging from a high degree of modification in FIGURE1 to a low degree of modification in FIGURE 3.

The preferred mode of practicing the invention is described moreparticularly in the following examples, but it will be understood thatlimitation of the scope of the invention is not thereby intended.

Example Each of three portions of a single lot of sheeted prehydrolyzedsulphate chemical wood pulp was processed into viscose, using theconventional sheet steeping process and spun into filaments to obtainthe filament crosssectional specimens of FIGURES 1, 2 and 3.

In accordance with the conventional sheet steeping procedure for theproduction of viscose rayon, airdried sheets of prehydrolyzed sulfatechemical wood pulp having dimensions of 10 inches by 10 inches and athickness of 0.040 inch were employed, but it is understood that bulkpulp may be utilized in achieving the results de scribed herein.Approximately 5 pounds of said pulp sheets were used for each of thesamples produced. The sheets were placed in the steeping press with thepredominant lengthwise orientation of the pulp fibers in the press beingperpendicular to the bottom of the press.

An aqueous solution of 18.5% sodium hydroxide at room temperature wasintroduced into the steeping press until the press was filled to a levelone-half inch above the top of the sheets of pulp.

After one hour, the excess sodium hydroxide solution was drained off andthe steeped pulp was hydraulically pressed to a weight equal to 2.9times the weight of the air-dry pulp sheets.

The pressed and weighed alkali cellulose was then shredded for one hourat a temperature of 29 C. At the completion of the shredding operation,the alkali cellulose crumbs were aged for 21 hours at 17 C. in astainless steel aging can.

After aging, carbon disulfide (CS was added to the alkali cellulose inan amount sufficient to provide 36.7% CS based on the weight of thecellulose in the alkali cellulose. This xanthation operation was carriedout in a conventional barrete for two hours at 29 C. The barrete wasthen unloaded and the xanthate transferred to a Vissolver (a jacketedvessel containing a high speed mixer) which contained caustic, water andthe specific modifier in an amount necessary to result in a viscosecontaining 6.6% cellulose, 6.4% sodium hydroxide and 1.9% sulfur andcontaining 0.5% based on the bone dry weight of the cellulose containedin the viscose of a chemical additive selected from the family ofchemical additives of this invention as more fully hereinbcforeindicated. The viscose solution was then mixed for two hours in theVissolver.

After filtering, wherein the viscose containing each of the additives ofthis example displayed substantially the same high degree offilterability, the viscose thus prepared was aged, or ripened, to aHottenroth index of 21 and extruded thru a spinneret into a spin bathcontaining 6.6% sulphuric acid, 19.2% sodium sulfate and 4.5% zincsulfate at 65 C. and then conducted through a second stretching bathcontaining 2.5% sulfuric acid at 95 C. wherein the yarn was stretched84%. The spinning speed of the pot spinning machine was 51 meters perminute. Although the spins of this example were carried out in a batchprocedure, the results will be the same when the fibers of varyingdegrees of modification are prepared continuously and sequentiallywithout purging the spinning equipment.

For the purposes of illustrating the present invention, the chemicaladditives used in the example were each prepared by random reaction ofdisproportionated rosin (Resin 731-D) with a mixture of ethylene oxideand 1,2-propylene oxide, the total oxides used being four times theamount of rosin by weight, and differed only in the proportional amountsof ethylene oxide and 1,2-propylene oxide content, and it is understoodthat the described results are substantially the same when thesequential com pounds with either ethylene oxide or propylene oxideterminal are employed.

The three additives of FIGURES 1, 2 and 3 employed to produce thesamples of this example were designated in that order as L-1180-2,L-l1882 and L-1190-2 and contained 85%, 70% and 40% respectively ofethylene oxide in the mixed oxide portion of their composition with thebalance of the mixed oxide chain consisting of 1,2-propylene oxide. Thefilaments spun and examined in the hereinbefore described manner fromthe three samples are represented in the same order in FIGURES 1, 2 and3 of the drawing. It is quite clear therefore, that as the percentage ofethylene oxide in the chemical additive is progressively decreased, andthe percentage of propylene oxide correspondingly increased, the extentof skin formation is reduced, as illustrated by the reduction in thesuccessive figures of the thickness of the filament skin.

L-1188-2 which is typical of the random type condensation products usedin the example was prepared in the following manner:

One of the reactants employed was a disproportionated rosin containing amajor proportion of dehydroabietic acid together with minor proportionsof dihydroabietic acid and tetrahydroabietic acid. Thisdisproportionated rosin is commercially available under the trade nameRosin 731-D and is prepared by heating tall oil to elevated temperaturesover extended periods of time in the presence of a suitable catalyst.The other reactants were 1,2-propylene oxide and ethylene oxide mixed inamounts of 70% ethylene oxide and 30% propylene oxide by weight. Thereaction was carried out in a jacketed vessel in the presence of sodiumhydroxide as a catalyst.

Sixteen pounds of the mixture containing ethylene oxide and1,2-propy1ene oxide in the aforementioned 70-30 weight ratio were addedto 4 pounds of disproportionated rosin containing 10 grams of sodiumhydroxide beginning at a temperature of 153 C. and continuing to atemperature of 158 C. and a final pressure of 70 psi. over a period of45 minutes during which time the mixed oxides were gradually added tothe jacketed vessel.

The resultant product contained four parts of mixed 9 oxides to one partof disproportionated rosin with the random oxide chain consisting of 70%ethylene oxide and 30% 1,2-propylene oxide and when employed in theprocessing of a prehydrolyzed chemical sulfate wood pulp into viscoserayon significantly modified the cross sections of the rayon filamentsobtained.

The sequential type condensation products which find use in the practiceof this invention are prepared in a like manner, except that the1,2-propylene oxide and ethylene oxide are introduced into the reactionvessel sequentially with either the ethylene oxide or the 1,2-propyleneoxide being terminal and the proportions of oxides to rosin and to eachother being adjusted within the range hereinbefore described for theproduct desired.

The chemical additives of this invention may be added to the celluloseat any convenient stage of pulp sheet formation or viscose processingprior to the extrusion of the viscose. For example, they may be added tothe pulp during the formation of the pulp sheet, after formation of thesheet but prior to completion of drying the sheet or after the sheet hasbeen formed and dried. The chemical additives, alone Orin admixturemaybe sprayed onto the entire surface area of the sheet or be applied tothe sheet as narrow stripes.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. In the manufaotureof regenerated cellulose filaments fromprehydrolyzed sulphate chemical wood pulp by the viscose process, thestep of incorporating in the viscose a modifying agent capable ofcontrolling the skin to core ratio and cross-section shape of filamentsspun from the viscose, said agents consisting essentially of ethyleneoxide-1,2-propylene oxide esters of 'disproportionated rosin in amountfrom 0.5% to 3.5% by weight of the bone dry pulp, the oxides beingpresent in the esters in amount from 1.5 to 9 times the amount of rosinby weight, and the ethylene oxide constituting from 40% to 85% of thetotal oxide Weight of the esters and being adjusted within the saidrange to obtain a desired skin to core ratio and cross-section shape inthe filaments.

2. The method of claim 1 in which the modifying agent is added at anystage in the process prior to the completion of steeping in the slurryviscose process and prior to the completion of shredding in the sheetsteeping viscose process to provide improved filtration.

3. The method of claim 1 in which the modifying agent is added tosheeted prehydrolyzed sulphate pulp.

4. The method of claim 1 in which the amount of agent is about 0.5% byweight of the pulp.

5. In the manufacture of regenerated cellulose filaments fromprehydrolyzed sulphate chemical wood pulp by the viscose process, thesteps of spinning the filaments from viscose containing, as a modifyingagent capable of controlling the skin to core ration and cross-sectionshape of filaments spun from the viscose, an ethylene oxide-1,2-propylene oxide ester of disproportionated rosin in amount from 0.5% to3.5% by weight of the pulp, the oxides being present in amount from 1.5to 9 times the amount of rosin by weight, and the ethylene oxide fallingwithin the range from 40% to of the total oxide Weight, and duringspinning substituting for the viscose containing said agent viscosecontaining an agent differing from the first mentioned agent only inhaving a different proportion of ethylene oxide to total oxide weightwithin said percentage range to change the skin to core ratio andcross-section shape alfected in the filament by the first agent, thesaid substitution being made prior to the spinnerets and without purgingthe system before said replacement substitution.

6. Prehydrolyzed sulphate chemical pulp for mom the manufacture ofregenerated cellulose filaments by the viscose process, said pulp havingincorporated therein an ethylene oxide-1,2-propylene oxide ester ofdisproportionated rosin in amount from 0.5% to 3.5% by weight of thepulp, the oxides being present in amount from 1.5 to .9 times the amountof rosin by weight, and the ethylene oxide constituting from 40% to 85%of the total oxide weight and being, adjusted within the said range toobtain a desired skin to core ratio and crosssectional shape infilaments spun from viscose prepared from said pulp.

References Cited in the file of this patent I UNITED STATES PATENTS Re.24,486 Mitchell June 10, 1958 2,784,107 Tallis Mar. 5, 1957 2,792,313Charles et al. May 14, 1957 2,813,038 Edwards Nov. 12, 1957 FOREIGNPATENTS 1,173,991 France Mar. 4, 1959 OTHER REFERENCES Huang et al.: J.Chem. Soc. Japan, Ind. Chem. Sect, vol. 56, pages 807-809 (1953), CA,vol. 49, 75430.

1. IN THE MANUFACTURE OF REGENERATED CELLULOSE FILAMENTS FROM PREHYDROLYZED SULPHATE CHEMICAL WOOD PULP BY THE VISCOSE PROCESS, THE STEP OF INCORPORATING IN THE VISCOSE A MOCIFYING AGENT CAPABLE OF CONTROLLING THE SKIN TO CORE RATIO AND CROSS-SECTION SHAPE OF FILAMENTS SPUN FROM THE VISCOSE, SAID AGENTS CONSISTING ESSENTIALLY OF ETHYLENE OXIDE- 1,2-PROPYLENE OXIDE ESTERS OF DISPROPORTIONATED ROSIN IN AMOUNT FROM 0.5% TO 3.5% BY WEIGHT OF THE BONE DRY PULP, THE OXIDE CONSTITUTING FROM 40% TO IN AMOUNT FROM 1.5 TO 9 TIMES THE AMOUNT OF ROSIN BY WEIGHT, AND THE ETHYLENE OXIDE CONSTITUTING FROM 40% TO 85% OF THE TOTAL OXIDE WEIGHT OF THE ESTERS AND BEING ADJUSTED WITHIN THE SAID RANGE TO OBTAIN A DESIRED SKIN TO CORE RATIO AND CROSS-SECTION SHAPE IN THE FILAMENTS. 